The Development Of Microprocessor-Based Protection For Shunt Reactor Applied To Ultra High Voltage Line

A shunt reactor, which can compensate charging power, restrain the power frequency overvoltage, and decrease secondary arc capacitance current during single-phase reclosing in lines, is an important electrical equipment in Ultra High Voltage (UHV) power system. With the increasing popularity of UHV network, the shunt reactor plays a more and more important role in improving the stability, security and economy of the network. However, the fault rate of the shunt reactor is relatively high while its existing protectors have shortcomings such as low sensitivity in inter-turn protection and unsatisfactory integrative performance. Therefore, it is of great necessity and significance to develop more advanced protective relaying for UHV line reactor. This paper first analyzes the existing application of UHV line shunt reactor in power systems as well as the present situation and future development of microprocessor-based reactor protection. Then an integrated design of protection system is proposed according to the requirements in the protection of UHV line shunt reactor. The paper gives a detailed explanation to the major designing principles and function config of the system as well as its hardware construct. Next, according to the faulty mechanism of reactors and the config experiences of reactor protection, the paper discusses the protective principles of UHV line shunt reactors. It also puts forward the calculating means according to related electrical parameters and analyzes the means theoretically. To improve most of the reactor protection devices that have shortcomings in inter-turn protection, the paper puts forward a highly sensitive, reliable inter-turn protection system, which is made up of both negative-sequence and zero-sequence power direction relays and so can solve the problem of overcompensation, undercompensation and uncertain compensation degree in inter-turn protection that is based on the compensation principle. Furthermore, according to the characteristics of different differential protection principles, the system adopts a plan of integrating these principles so as to increase the sensitivity and reliability of differential protection. The paper introduces systematically the mechanism and operation of the integrative differential protection. The ground protection unit is the core and basis of microprocessor reactor protective system. The paper explains in great details the designing principles, realizing methods, flow process, primary module functions and communication means of the protection unit. Because the protective program follows the designing idea based on protection logic diagram and adopts a layered modular structure, it is flexible in the config of protection functions and easy to maintain in different situations of field operation. Finally, the paper describes the static simulation experiments for the protection system of UHV line shunt reactor. The results of the experiments and some specific problems are analyzed. The experiments show that the performance of the protection has achieved the goals of the system design.